Question: Gabriela was assigned pages 40 through 78 for homework last week. If Gabriela read all of the pages she was assigned, how many pages did she read?
Answer: Instead of counting pages 40 through 78, we can subtract 39 from each number so we instead consider pages 1 through 39. We see that Gabriela read 39 pages. Notice that she read 39 and not 38 pages.